1. Field of the Invention
The present invention relates to a device for varnishing printed sheets in a printing machine, or printing press. The printing machine includes a varnish pan, a dipping roller and a metering roller for transferring varnish onto a varnishing cylinder. The dipping roller and the metering roller include a drive mechanism that can be connected to the machine drive by an overrunning clutch. The printing press also includes an auxiliary motor through which the dipping roller and the metering roller can be driven, even when the machine is at a standstill. The auxiliary motor is connected to the dipping roller and/or the metering roller through a torque transmitting device that does not include a rigid, rotary connection therein.
2. Background Information
Printing presses in which the present invention may be employed are well known. U.S. Pat. application Ser. No. 07/482,260, which is now allowed and which will issue as U.S. Pat. No. 5,010,820 on Apr. 30, 1991, discloses one such printing press.
Printing machine, or printing press, varnishing units are disclosed in German Patent Publication Number 33 24 096 C2. Also, a drive of a varnishing unit that can be connected to the machine drive of a printing press through an overrunning clutch is disclosed in German Patent Publication Number 36 38 469 A1. This disclosed device provides an auxiliary motor for driving the dipping roller and the metering roller when the machine is at a standstill.
Also, German Patent Publication Number 36 38 469 A1 discloses an electromagnetic clutch through which a dipping roller and a metering roller are driven and rotated by an electromotor when the machine is at a standstill to prevent the varnish from drying up on the rollers. A rigid drive mechanism for the rollers is not needed in the device disclosed in this patent publication. However, the electromagnetic clutch mechanism and its switching apparatus disclosed in this patent publication are expensive and not very economical to construct and/or operate.